Method of controlling welding current in direct-current resistance welding machine

摘要

A workpiece is welded successively at a plurality of welding points by a direct-current resistance welding machine with a constant current in a welding current supply period at each of the welding points, and the constant current is varied depending on whether expulsions are produced on the workpiece when it is welded, to determine an expulsion-producing limit current value as a maximum current beyond which expulsions will be produced. The workpiece is welded with a first stepped welding current having a first current value that is smaller than the expulsion-producing limit current value by a predetermined value and a second current value that is greater than the expulsion-producing limit current value, and an average current value higher than the expulsion-producing limit current value, and also with a second stepped welding current having a variation of the second current value based on whether expulsions are produced or not on the workpiece when it is welded with the first stepped welding current.